The present invention is directed to an apparatus for attaching a cranial flap to a skull, from which the cranial flap was removed, during surgery.
Surgical operations involving the human skull, such as brain surgery or craniofacial surgery, require that a section of the skull be removed. Typically, a number of burr holes are first drilled into the skull and which outline the section of the skull to be removed. A cutting tool is then inserted into one of the burr holes and a cut, or osteotomy, is made from one burr hole to then next burr hole until a loop is completed. The loop of osteotomies forms an opening in the skull and defines the section of the skull to be removed. The section of the skull to be removed is commonly referred to as a cranial flap. Because the blade on the cutting tool typically has a width of 1-3 mm, a kerf of that width is formed between the opening in the skull and the cranial flap. Due to the width of the kerf, the periphery of the cranial flap is smaller than the opening in the skull.
When the surgical procedure inside the skull is complete, the cranial flap must be replaced in the opening in the skull and re-attached to the skull. A number of methods and attachment devices are known for re-attaching the cranial flap to the skull. One known method uses stainless steel wire as a suture material for wiring the cranial flap and the skull together. Some of the known devices include plates and associated screws made from either titanium or a bioabsorbable polymer. Other known devices employ rivet-type fasteners made of titanium or a biocompatible polymer such as acetyl resin.
One of the disadvantages of several of the known attachment devices is that a portion of the device rests on top of, and thus protrudes from, the outer surface of the skull, resulting in visible and unsightly bumps under the patient""s skin. Another disadvantage of the known rivet-type fasteners is that a portion of the fastener remains in contact with the dura, as it is generally believed that such contact with the dura could be potentially harmful. Thus, it is desirable to provide an attachment device which is disposed entirely within the kerf and thus does not contact the dura nor protrude beyond the outer surface of the skull.
The present invention is an apparatus for attaching a cranial flap to a skull during surgery. The cranial flap and the skull are spaced apart by a kerf defined by a first kerf edge on the cranial flap and an oppositely disposed second kerf edge on the skull. The apparatus comprises at least one attachment device comprising first and second members that are movable relative to each other along an axis. The first member has oppositely disposed first and second surfaces for engaging the first and second kerf edges, respectively. The first member further includes an opening extending along the axis. The second member has oppositely disposed third and fourth surfaces for engaging the first and second kerf edges, respectively. A shaft member connects the first and second members. The shaft member is attached to the second member and extends through the opening in the first member. The at least one attachment device is positionable in the kerf and movable from a first condition in which the first surface on the first member and the third surface on the second member are not engaged with the first kerf edge and the second surface on the first member and the fourth surface on the second member are not engaged with the second kerf edge to a second condition in which the at least one attachment device is wedged in the kerf by circumferential pressure and frictional engagement between the first and third surfaces and the first kerf edge and by circumferential pressure and frictional engagement between the second and fourth surfaces and the second kerf edge to thereby attach the cranial flap to the skull and prevent the cranial flap from moving relative to the skull.